Because of their low-cost and small size they can then be shipped to activists and NGO's in areas where free-speech is difficult.

"This is especially useful for activist organizations, human rights organizations, any group composed of a few dozen people who need to have an internal secure communication service," said Mr Kobeissi.

Small, portable Raspberry Pi computers set up to run Cryptocat, he believes, may be a quick way to build such a service.

An interesting consequence of Moore's Law and the ready availability of free software is that powerful computers can now be produced for just tens of dollars, and in an extremely small package. The low cost means that organizations supporting activists can send in many such systems to countries with human rights problems, and replace them if they are discovered and confiscated or destroyed. The size makes it much easier to import them discreetly, as well as to conceal them in countries that try to keep computing under tight control.

And it's not just the Raspberry Pi that will be making this possible. Its high-profile success is likely to mean that in due course other systems will be produced that are cheaper and smaller. That will ensure they are even more popular with the educational market and hackers -- and even more problematic for oppressive regimes.